This invention relates generally to particulate material coolers, and more particularly to grate plates used in cooling hot particulate material.
There are presently particulate material coolers, such as those used to cool hot cement clinker after it is discharged from a kiln. These systems commonly have tiered rows of grate plates descending from a kiln outlet to a cooled material outlet. The grate plates in each row lie closely adjacent to one another to form a substantially continuous working surface for the heated material. Each row of grate plates is attached to a respective support structure. In such an arrangement, the rear portion of each grate plate is overlapped by a grate plate of the row above, and the forward portion of each grate plate overlaps the rear portion of a grate plate in the row below. It is also known to oscillate some of the rows of grate plates back and forth to encourage the forward flow of heated material through the cooler. As hot particulate material exits the kiln and enters the cooler, gravity and oscillation of some rows of the grate plates causes the material to generally move forward, descending from one tier to the next while the material is cooled. In some coolers, cooling is effected, in part, by a stream of cooling air flowing from the support structure up through the bottom of the grate plates.
Grate plates constructed to permit cooling air to flow through them from beneath may have openings in an exposed upper surface of the grate plate opening directly to the underside of the grate plate. Flow of air to any particular row of grate plates cannot be controlled with this type of grate plate. Other grate plates are constructed to permit the flow of air to each row of grate plates to be independently controlled. A controlled flow grate plate is generally boxshaped, and defines an internal plenum opening to the underside of the plate only at the bottom rear of the grate plate. Cooling air must pass into the plenum through the rear opening and thence forward through longitudinally extending ducts in the grate plate to the openings to the upper surface of the grate plate. The grate plate is attached to a channel beam having an open top over which the rear opening of the grate plate is disposed. Air flow through the channel beam and out the grate plates mounted thereon can be controlled independently of other channel beams mounting rows of grate plates in the cooler.
A problem associated with prior controlled flow grate plates is the relatively short life span due to thermal effects. The exposed front wall of each grate plate is subject to relatively high temperatures from the heated material continually flowing over the forward portion of the grate plate. In cooling systems which have oscillating rows of grate plates, the front walls of the moving grate plates are subject to high temperatures when pushing the heated material forward.
It is known to provide a duct in the plenum extending laterally along the front wall of the grate plate. Any cooling air not forced out of the openings in the longitudinally extending ducts reaches the front wall of the grate plate and provides cooling to the front wall. Other grate plates, having no openings to their upper surfaces, channel cooling air directly to the front wall, and forwardly out through openings in the front wall. Drawbacks associated with these approaches are that either much of the coolest air is released through the openings in the longitudinally extending ducts before it reaches the front wall, or the air is released through the front wall without cooling the heated material on the top surface of the grate plate.